I don’t want to rule out that this is individual hardware (SD card) failure, but want to mention it nevertheless:
I updated to v1.4 (dev) on my Fairphone 3+ earlier today. Since the end of a long walk this afternoon, having listened to 2+ hours of music from my SD card (formatted as external/portable) via VLC without issues, I keep getting “several media files cannot be played” (my translation from German) error messages, even when VLC is paused. I can eventually restart VLC and play music files again, but the error messages seems to stay until a reboot. The problem re-occured after 1-2 reboots.
Additional info: My VLC app only got an update itself a few days ago.